Radial fan

ABSTRACT

A radial fan, preferably a high-speed radial fan, includes a blower wheel, a housing which receives a rotor and a stator of an electrical drive of the blower wheel shaft, and a cooling system. To develop one such radial fan in terms of the cooling system required, paths for a first cooling medium and a second cooling medium are provided in the housing, the second cooling medium being cooled by the first cooling medium as provided for by the housing, and the paths are separated from each other by intact material walls of the housing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and Applicants claim priority under35 U.S.C.§§120 and 121 on U.S. application Ser. No. 11/921,714 filed onJan. 9, 2008, which application is a national stage application under 35U.S.C.§371 of PCT Application No. PCT/EP2006/062756 filed May 31, 2006,which claims priority under 35 U.S.C.§119 from German Patent ApplicationNo. 10 2005 025 865.4 filed Jun. 6, 2005, German Patent Application No.10 2005 025 857.3 filed Jun. 6, 2005, and German Patent Application No.10 2005 025 858.1 filed Jun. 6, 2005, the disclosures of each of whichare hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a radial fan, preferably high-speed radial fan,having an impeller and a housing, the housing accommodating a rotor anda stator of an electric drive for the impeller shaft, and a coolingmeans being provided.

2. The Prior Art

Radial fans of the type in question, in particular radial fans whichrotate at high speeds, are known and are used, for example, inconjunction with lasers. Since considerable thermal loads have to bedissipated here, a cooling means is provided.

SUMMARY OF THE INVENTION

In respect of the prior art described above, it is considered to be anobject of the invention to improve further a radial fan of the type inquestion in respect of the cooling required.

Since it is also the case with such radial fans that considerablethermal loads have to be dissipated, it is also an object of theinvention to configure such a radial fan advantageously in respect ofthe necessary cooling means.

Furthermore, it is also intended for the impeller, which is driven by anelectric drive accommodated in the housing, to be configuredadvantageously in safety terms.

The first object is achieved first and foremost by the invention in afirst aspect which is based on the fact that paths are provided in thehousing for a first cooling medium and a second cooling medium, forcooling of the second cooling medium by the first cooling medium bymeans of the housing, and that these paths are separated from oneanother by uninterrupted material walls of the housing. This accordinglyprovides a sealing-free system which allows two-fold cooling of theradial fan, in particular of the housing and/or the rotor/stator regionthereof, namely by a first cooling medium and a second cooling medium,the second cooling medium serving for secondary cooling, while the firstcooling medium provides primary cooling. The paths of the two coolingmedia are separated hermetically from one another, this separation beingachieved by way of material walls of the housing itself. For thispurpose, the fan housing preferably consists of a casting material suchas, in particular, a lightweight material, for example aluminum, whichis formed with thick walls.

The subject matters of further developments are explained hereinbelow.

Thus, in a preferred configuration, it is provided that the paths in thehousing run at an angle in relation to one another, that is to say, whenseen three-dimensionally, they are not parallel to one another. Rather,the paths of the two cooling media, in a projection, enclose for examplean acute angle, which results, in a projection, in the cooling-mediapaths crossing. A preferred configuration is one in which the paths runperpendicularly to one another, in which case, for example, paths of thefirst cooling medium extend parallel to the impeller-shaft axis, whilethe paths of the second cooling medium run substantially in thecircumferential direction in relation to the impeller-shaft axis. Thepaths are formed in the housing in the casting process and/or as bores.It is thus possible, during the casting operation for producing thehousing, to form these paths at the same time. As an alternative, inparticular in the case of a solid housing component, the paths may beformed by bores. The paths of the first cooling medium are preferablydisposed in the outer wall of the housing, in a cross-sectionallychamber-like housing recess. This chamber-like housing recess is formedin the housing preferably during the production process, therefore, inparticular, during production by casting. The chamber-like housingrecess is open in the radially outward direction in relation to thehousing and, furthermore, two circumferentially distributed paths of thefirst cooling medium are routed in the chamber-like housing recess.Correspondingly, two consecutive paths of the first cooling medium openout, preferably in the circumferential direction, in a housing recess.In a preferred configuration of the subject matter of the invention, itis provided that three or more chamber-like housing recesses areprovided over the circumference, further preferably four such housingrecesses, which are distributed uniformly in the circumferentialdirection. In the axial direction of the housing, the chamber-likehousing recesses are bounded by integral walls of the housing. Also inthe circumferential direction, two adjacent chamber-like housingrecesses are separated from one another by a solid portion of thehousing, which solid portion has at least one path for the first coolingmedium passing through it in order to connect these adjacentchamber-like housing recesses. The chamber-like housing recesses areclosed by a covering extending in the axial direction of the housing. Asa result, the chamber-like housing recesses, which are enclosed on allsides, form part of the path for the first cooling medium. Accordingly,taking account of housing recesses distributed over the circumferenceand of paths which are provided in each case between two adjacenthousing recesses, and pass through the housing portion, a circuit isprovided in the circumferential direction of the housing. The coveringmay be in the form of a tubular part which encloses the housing. As analternative, it is also possible for plate-like individual coverings tobe associated with each chamber-like housing recess. The significantfactor here is for each individual housing recess to be closed in asealing manner. One chamber-like housing recess is preferably formed asa cooling-medium infeed and a further chamber-like housing recess isformed as a cooling-medium discharge. Accordingly, associated with thesehousing recesses, or the coverings or covering portions which close thesame, there are preferably provided couplings or the like for theconnection of external pipe or hose portions. It is also proposed thatthe housing be cylindrical, one end being associated with the impellerand the other end being closed via a foot part, for hermetically sealingthe housing, which contains the paths for the cooling media andaccommodates the electric drive for the impeller shaft. For sealingclosure, it is further provided that the other end has a steppedformation, and the foot part is stepped correspondingly. In particularthis stepped formation results in sealing of the second cooling-mediumpath with respect to the exterior. Furthermore, the foot part may form,at the same time, in the direction of the housing interior, portions ofpaths for the second cooling medium. In addition, the foot part may haveplug-like inlets for the power supply, on the one hand, and possibly thesensor system and associated electronics, on the other hand.Cooling-related advantages are achieved in that the paths of the firstcooling medium run further toward the inside, as seen in the radialdirection, than the paths of the second cooling medium at least in theregion between the chamber-like housing recesses, the second coolingmedium also passing through the interior of the housing. The paths ofthe second cooling medium thus preferably run parallel to the axialalignment of the impeller shaft in the region of the solid housingportions which separate two circumferentially adjacent, chamber-likehousing recesses from one another. These solid housing portions haveboth the paths of the first cooling medium passing through them in onedirection and the paths of the second cooling medium passing throughthem preferably perpendicularly thereto. As an alternative, it is alsopossible for the paths of the first cooling medium to be providedfurther toward the outside, as seen in the radial direction, than thepaths of the second cooling medium. Furthermore, in a preferredconfiguration, it is provided that the paths of the first cooling mediumrun in the circumferential direction in relation to the impeller-shaftaxis. A plurality of paths which are positioned axially one behind theother, and are brought together in each case in the chamber-like housingrecesses, are provided here. This multiplicity of paths for the firstcooling medium is restricted, further preferably, to the region of theelectric drive in the housing. The paths of the second cooling mediumextend, further preferably, over more or less the entire axial length ofthe housing from the impeller to the foot part provided opposite. Thus,in a development of the subject matter of the invention, it is providedthat the paths of the first cooling medium, predominantly for thepurpose of dissipating the power loss of the stator, are brought closeto the stator such that the thickness of the housing material remainingbetween the paths and the stator which is to be cooled corresponds to,or is less than, a cooling-medium-path diameter. It is also proposedthat axial bores which correspond to the paths for the second coolingmedium, and are used for accommodating electric lines, be provided. Itis thus extremely easy to provide for axial lead-through of electriclines while, at the same time, ensuring insulation in relation to thefirst cooling system.

The object in respect of the cooling system is achieved first andforemost by the invention in another aspect which is based on the factthat cooling in particular of the drive is achieved by a partial gasstream separated off from the gas which is to be compressed. This givesrise to a cooling system by means of which, with hermetic closure withrespect to the exterior, considerable thermal loads can be dissipated.For this purpose, the gas which is compressed in any case by the radialfan is used for self-cooling of the fan drive, in particular of thehousing region which accommodates the rotor and stator, in which casethe branched-off partial gas stream, which serves for cooling purposes,is channeled specifically through the housing and/or through therotor/stator region. In addition, this branched-off partial gas stream,after passing through the cooling route, is fed back to the main gasstream developed by the fan impeller. Hermetically sealed cooling of theradial fan with respect to the exterior is achieved as a result. In apreferred configuration, it is thus possible to realize a sealing-freesystem.

The subject matter of a further development is explained hereinbelow.

Thus, in a preferred development of the subject matter of the invention,it is provided that cooling of the partial gas stream takes place by wayof contact with the housing wall, which, for its part, is activelycooled. It is thus possible for the partial gas stream to be channeledthrough channels which are appropriately provided in the housing, andalong the walls of which heat exchange takes place.

The invention also relates to a radial fan, an improvement in thecooling capacity being achieved in that a partial gas stream separatedoff from the gas which is to be compressed is channeled, followingseparation, into paths of a cooling-channel housing, which, for itspart, is actively cooled at least indirectly. This results in(preliminary) cooling of the partial gas stream, in first instanceprimarily by way of contact with the housing walls which delimit thehousing paths and also, secondarily, by way of separate active coolingof the cooling-channel housing and thus of the walls of the housingpaths. The housing has good thermal conductivity for this purpose and,further preferably, consists of a metal material, in particular alight-metal material, for example in the form of an aluminum casting. Inorder to improve the cooling capacity further, an active cooling meansfor the housing is also provided, this means absorbing, and dissipating,the heat which is given up by the partial gas stream via the housingwall.

The subject matters of further developments are explained hereinbelow.

The housing paths may be labyrinthine. This makes it possible to achievelarge-surface-area preliminary cooling of the partial gas stream by wayof contact with the housing wall in the labyrinthine housing path, thehousing paths, further preferably, leading radially inward from theoutside. It is also proposed that the partial gas stream be branched offfrom the main gas stream radially outside the impeller, in the region ofa diffuser, specifically preferably at the outlet from the diffuser. Useis made here of the difference in pressure which prevails, duringoperation of the radial fan, between the higher pressure at the diffuseroutlet and the lower pressure in the motor housing and/or in the regionwhere the partial gas stream re-enters the main gas stream at the outerperiphery of the impeller and/or at the diffuser inlet, in order thus toachieve an automatically operating partial gas cooling circuit withinthe fan housing. The partial gas stream is accordingly forced throughthe fan housing and the electric drive for cooling purposes. It isprovided that the partial gas stream is channeled radially inward infirst instance and then passes through the housing wall of the housingregion which accommodates the electric drive, thus preferably parallelto the impeller axis, furthermore a plurality of such channels or thelike for the partial gas stream being provided in the housing around theimpeller axis, as seen in cross-section. It is at that end of theelectric drive which is directed away from the impeller that the partialgas stream-is preferably channeled out of the housing into theinterspace between the stator and rotor, accordingly passing over thesurfaces of the rotor and stator for heat dissipation. As analternative, or also in combination therewith, it may be provided thatthe drive shaft is in the form of a hollow shaft, and that it is at thatend of the electric drive which is directed away from the impeller thatthe partial gas stream is channeled out of the housing into the driveshaft, in order to pass through the latter centrally in the direction inwhich the drive shaft extends, heat dissipation taking place by way ofcontact with the shaft wall. In the case of a combined solution in whichthe partial gas stream is channeled both through the drive shaft, in theform of a hollow shaft, and through the interspace between the statorand rotor, these two partial gas streams are preferably brought togetherdownstream of the rotor and/or stator, as seen in the flow direction,and furthermore the flow direction of the partial gas stream as itpasses through the interspace between the stator and rotor and as itpasses through the hollow shaft being counter to the flow direction ofthe partial gas stream which, coming from the labyrinthine housing path,passes through the housing in the direction of the end which is directedaway from the impeller. Finally, the partial gas stream is channeledback into the main gas stream at the radially outer periphery of theimpeller. A lower pressure prevails at this location than in theradially outer position in the region of the diffuser outlet, at whichthe partial gas stream is branched off from the main gas stream, and adifferential-pressure-controlled circuit is accordingly established. Ina preferred configuration of the subject matter of the invention, it isprovided that the active cooling means of the housing is in the form ofa water cooling means. This water cooling means, which forms a secondarycooling means, is separated hermetically from the gas cooling means,which forms the primary cooling means, furthermore basically asealing-free system being present. Finally, it is provided that the gasconsists of helium and/or nitrogen and/or is air and/or is a mixture oftwo or more of the gases mentioned.

The object, mentioned in the introduction, relating to the safety aspectis achieved first and foremost by the invention in another aspect whichis based on the fact that, in order to form a cage which encloses theimpeller, cage plates are provided on the cover side and underside ofthe impeller, and these cage plates are held together around theperiphery of the impeller by, for example, stud-like connecting means,at least the connecting means and the cover-side cage plate consistingof a hard and tough material such as steel. This configuration providesa safeguard against bursting. This prevents, in first instance in theevent of the impeller bursting, the cover-side housing part, whichconsists of a light-metal casting material, from being lifted off and/ordestroyed. Such a situation where the cover is lifted off and/ordestroyed would result in enlargement of the air gap which, in the caseof a radial fan, opens outward, and relatively large fragments of theruptured impeller could escape at high speed through this enlarged gap.This risk is countered by the provision of the cover-side cage plate,which consists of a hard and tough material such as steel, furthermore,for example, ST 50. This cover-side cage plate forms a protective shieldfor the cover disposed at the rear, that is to say on that side of thecage plate which is directed away from the impeller. It is also the casethat the cage plates provided on the cover side and underside of theimpeller are secured against displacement—both in the radial and in theaxial directions—stud-like connecting means being provided for thispurpose. These connecting means keep the cage plates at a predetermined,axial spacing. Since, according to the invention, these connecting meansalso consist of a hard and tough material such as steel, they are alsoprotected against being destroyed by fragments resulting from bursting.

The subject matters of further developments are explained hereinbelow.

It is thus provided that, in order to form the cover, the housing isdivided parallel to a plane of revolution of the impeller. Furthermore,it proves to be particularly advantageous if both cage plates consist ofa hard and tough material such as steel, furthermore, for example, suchas ST 50. As a result of this configuration, the cage enclosing theimpeller is formed entirely from a hard and tough material. The radialair-outlet gap as seen in thickness directions, that is to say asmeasured parallel to the impeller axis, is selected such that, in theevent of the impeller bursting, in the worst-case scenario only smallfragments can pass radially outward. Larger, and thus also moredangerous, fragments cannot pass through this annular gap since the cageprovided does not allow any widening of the gap. In addition to thecover mentioned, it is also possible for the housing to be in the formof a light-metal casting, and thus, furthermore, for example made ofaluminum. The cage plate which encloses the impeller on the undersidealso protects such a light-metal housing against being destroyed byfragments. In a preferred configuration, the connecting means arescrew-connected both in the housing and in the cover and, accordingly,additionally form a connection between the housing and cover which isresistant to fracture and impact. Force transmission in the event ofbursting takes place primarily via steel nuts which are screwed onto theconnecting means, support the cage plates at the rear and counteract anyenlargement of the gap between the cage plates. As an alternative to asteel nut, it is also possible for a steel collar to be formed on theconnecting means. A diffuser part is preferably disposed beneath thehousing cover, the cover-side cage plate being disposed between thehousing cover and the diffuser part. The connecting means here also passthrough the diffuser part for screw-connected engagement in the housingcover. In a development of the subject matter of the invention, it isprovided that a first housing part is disposed beneath the impeller anda cooling-channel cover is fitted on the side of the first housing partwhich is directed away from the impeller. The underside cage plate ispreferably disposed between the impeller and the first housing part. Inaddition, the first housing part may have cooling channels which areclosed by the cooling-channel cover disposed on the underside. Thehousing, which accommodates the electric drive for the impeller, isfastened on the first housing part, which forms a cooling-channelhousing. The connecting means are secured, at one end, in thecooling-channel housing and, at the other end, preferably in the housingcover, with the interposition of the two cage plates and of the diffuserand of the first housing part. For screw-connection, the connectingmeans, in a preferred configuration, are in the form of studs which havescrew threads at the ends. In addition, it is proposed that the cageplates be in the form of annular parts, further preferably with acage-plate internal diameter which is adapted to the external diameterof the impeller, and therefore, furthermore, with a slight oversize inrelation to the external diameter of the impeller. The radial extent ofthe annular part corresponds to a radial dimension of the impeller orless, and therefore, furthermore, approximately to a third, a quarter,half or also two thirds or three quarters or also even further fractionsof the radial extent. The impeller has blades, having different heightsin the radial direction, the gap formed by the cage plates overlappingonly part of the height of the blades, to be precise that part whichcorresponds at least to the height of the blades at their greatestradial extent. Accordingly, the gap between the cage plates is adaptedto the axial extent of the impeller or of its blade in the radiallyouter region.

Accordingly, the extent of the gap is only a fraction of the axiallymeasured overall height of the impeller, that is to say a fraction ofthe maximum height of the blades. The gap thus corresponds preferablyapproximately to half the maximum blade height, but, in addition, mayalso correspond approximately to a quarter, a third or also two thirdsto three quarters of the maximum blade height. In addition, it isprovided that the lower cage plate extends axially into a foot region ofthe blades, and, further preferably, engages beneath the impeller in theradially inward direction. Accordingly, the lower cage plate is providedwith a recessed portion which is adapted to the maximum external radiusof the impeller, and in which the impeller is positioned. That portionof the lower cage plate which is provided for engaging beneath theimpeller has a radial extent which corresponds approximately to thesmallest height of the blades at their greatest radial extent. In orderfor the cage to be resistant to fracture and impact, it is furtherprovided that, in the case of the impeller having a diameter of 100millimeters or more in the foot region, at least one connecting stud isprovided for each 25 millimeters of diameter. Accordingly, in the caseof an impeller having a diameter of 100 millimeters or more, at leastfour connecting studs are provided, and these, in addition, aredistributed uniformly over the circumference. In this respect, it isfurther preferred if, in the case of a diameter of 150 millimeters, sixor more connecting studs, for example seven, eight or ten connectingstuds, are distributed at uniform angles over the circumference, whichconnecting studs are all anchored preferably by screw-connection, at oneend, in the housing cover and, at the other end, in the cooling-channelcover.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail hereinbelow with reference tothe accompanying drawing, which merely illustrates exemplary embodimentsand in which:

FIG. 1 shows a perspective illustration of a radial fan according to theinvention;

FIG. 2 shows a perspective illustration corresponding to FIG. 1, butfollowing removal of a cover in order to expose a first cage plate;

FIG. 3 shows an illustration corresponding to FIG. 2, but followingfurther removal of the cage plate in order to expose a diffuser;

FIG. 4 shows a further illustration according to FIG. 1, but followingremoval of the diffuser in order to expose a second cage plate and animpeller;

FIG. 5 shows a further perspective illustration according to theillustration in FIG. 2, but following removal of the second cage platein order to expose a housing part containing a labyrinthine housingpath;

FIG. 6 shows an exploded perspective view of the radial fan, theelectric drive which is required for driving the impeller having beenleft out;

FIG. 7 shows the front view of the radial fan;

FIG. 8 shows the section through the radial fan along line VIII-VIII inFIG. 7;

FIG. 8 a shows the sectionally illustrated enlargement of the regionVIIIa in FIG. 8;

FIG. 9 shows the section along line IX-IX in FIG. 7;

FIG. 10 shows the cross-section along line X-X in FIG. 9, here too withthe electric drive having been left out;

FIG. 11 shows a sectional illustration corresponding to FIG. 9, butrelating to an alternative embodiment of the radial fan, the cage platesand the housing cover having been left out;

FIG. 12 shows the cross-section along line XII-XII in FIG. 11;

FIG. 13 shows a perspective illustration of the fan housing of thesecond embodiment; and

FIG. 14 shows a further perspective illustration of the housing with acovering which encloses the housing having been left out.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A first embodiment of a radial fan 1, which is in the form of ahigh-speed radial fan, will be illustrated and described in firstinstance with reference to the illustrations in FIGS. 1 to 6.

This radial fan 1 has a drive portion A and a fan portion B associatedtherewith.

The drive portion A has a housing 2. The latter is in the form of alight-metal casting and, in the end region which is directed toward thefan portion B, is hollow-cylindrical with a round cross-section. Thiscross-section continues substantially over the entire longitudinalextent of the housing 2, but with plane surfaces 3, which are positionedin the manner of secants in relation to the circle cross-section, beingformed. Four plane surfaces 3 are provided in this respect, and theseare disposed in a square arrangement as seen in the cross-sectionaccording to the illustration in FIG. 10. Correspondingly, the cornerregions of the square cross-section are rounded by the radius of theannular housing portion.

In the housing 2, an electric drive 4 is accommodated, having a stator 5and a rotor 6. The latter forms a drive shaft 7 in the form of a shaft,specifically a hollow shaft.

The drive-shaft axis x coincides with the longitudinal axis of thehousing. Mounting of the drive shaft 7 is effected via bearings (notillustrated specifically), for example magnetic bearings.

The drive shaft 7 extends beyond the annular end portion of the housing2, as seen in plan view, for the rotationally fixed connection of animpeller 8 of the fan portion B.

That end of the housing 2 which is directed away from the impeller 8 isclosed by a foot part 9. For this purpose, the housing 2, which isgenerally in the form of a hollow body, has a stepped formation 10, inwhich the correspondingly stepped foot part 9 is positioned in a sealingmanner.

The fan portion B is made up substantially of rotationally symmetricalcomponents disposed one behind the other along the shaft axis x.

The fan portion B thus has, in first instance, a cooling-channel cover11. This cooling-channel cover 11 is followed—as seen in the shaft-axisdirection away from the housing 2—by a cooling-channel housing 14, whichforms a first housing part 13. This cooling-channel housing isscrew-connected to the cooling-channel cover 11 in order to cover thatside of the cooling-channel housing 14 which is directed toward thehousing 2.

A further annular part which is designated by the numeral 15 forms aconstituent part of the drive portion A and is screw-connected to thehousing 2.

It is also the case that the first housing part 13 or thecooling-channel housing 14 is formed as an annular component in planview, having a free internal diameter which is reduced in relation tothe annular cooling-channel adapter part 15. The internal diameter ofthe cooling-channel adapter part 15 is adapted to the free internaldiameter of the facing annular housing portion.

In addition, the free internal diameter of the cooling-channel housing14 is selected to be somewhat smaller than the maximum external diameterof the impeller 8, which is further positioned on that side of thecooling-channel housing 14 which is directed away from thecooling-channel cover 11, and is connected there to the drive shaft 7 ina rotationally fixed manner.

Starting from a central region, the impeller 8 has radially outwardlyextending blades 16, which have different heights in the radialdirection, that is to say decrease in height in the radially outwarddirection. The radially outwardly oriented peripheral edges of theblades 16 are approximately concave in cross-section, for exampleaccording to the illustration in FIG. 8, and a height h′ selected forthe blades 16 in the region of the greatest radial extent of the blades16, that is to say in the foot region of the impeller 8, this footregion being directed toward the cooling-channel housing 14, correspondsapproximately to a quarter of the axially measured overall height h ofthe impeller 8.

That side of the cooling-channel housing 14 which is directed toward theimpeller 8 is provided with a central, disk-like recessed portion 17.This has a larger diameter than the foot region of the impeller 8.

In the recessed portion 17, a cage plate 18 is located, which is annularin plan view. This cage plate consists of a hard and tough material, forexample ST 50 steel. The external diameter of this cage plate 18 isadapted to the internal diameter of the recessed portion 17 in thecooling-channel housing. The internal diameter of the cage plate 18 isselected such that the impeller 8 has its greatest radial extent, thatis to say the foot region, positioned in a freely rotating manner, witha small gap being left, in the annular space of the cage plate 18.Furthermore, the cage plate 18 is formed such that it engages beneaththe impeller 8 in a radially inward direction. Correspondingly, anannular collar 19, which is less thick than the overall thickness of thecage plate 18, extends radially inward from the inner annular edge ofthe cage plate 18.

A diffuser 20, which is likewise formed as a rotationally symmetricalcomponent, is secured on that side of the cage plate 18 which isdirected away from the cooling-channel housing 14. This diffuser has acentral inlet cross-section into which the impeller 8 penetrates. Inaddition, a radially outwardly opening annular gap 21 which remainsdirectly above the cage plate 18 has diffuser blades 22 passing throughit in a known manner, these diffuser blades evening out the gas flowwhich passes out radially and, in the process, increasing the gaspressure in the radially outward direction.

It is also the case that the diffuser 20 has on the upper side, which isdirected away from the cage plate 18, an annular recess 23, which isoriented concentrically in relation to the shaft axis x. In this recess,a further cage plate 24 is located, which in the exemplary embodimentillustrated has a thickness, measured in the shaft-axis direction x,which corresponds approximately to two thirds of the thickness of thecage plate 18, which is provided on the underside of the diffuser 20.This cage plate 24 also consists of a hard and tough material such as ST50 steel.

Finally, disposed on the cage plate 24 is a housing cover 25 which alsoengages over the funnel-like intake portion of the diffuser 20 and formsthe axial gas inflow. This housing cover as well as the diffuser 20and/or the cooling-channel housing 14 and/or the cooling-channel adapterpart 15 and the housing 2 preferably consist of a light-metal castingmaterial, for example aluminum.

The housing cover 25 and cooling-channel housing 14 are braced inrelation to one another with the interposition of the two cage plates 24and 18 and the diffuser 20. For this purpose, use is made of, in theexemplary embodiment illustrated, seven connecting means 26 which aredistributed uniformly over the circumference and are in the form ofstuds 27 which have screw threads at least at the ends. These studs arescrewed, at one end, to a limited extent into corresponding threadedbores of the cooling-channel housing 14, and then form guiding andsecuring studs which are correspondingly parallel to the shaft axis x.These studs 27, which are used in the manner of stay bolts, have radialcollars 27′ which are positioned in correspondingly shaped recesses inthe cooling-channel housing 14 such that they are substantially flushwith the associated surface of the cooling-channel housing 14. Duringassembly, first of all the lower cage plate 18 is pushed on in the axialdirection over these studs 27—after which the impeller 8 is initiallysecured on the drive shaft 7—and then the diffuser 20 and the cage plate24 are pushed on in the axial direction over the studs 27. This isfollowed by the cage plate 24 being secured axially by means of steelnuts 27″ which are screwed onto the studs 27 and are positioned incorrespondingly formed recessed portions of the housing cover 25, whichis the last to be placed in position. The stud ends passing through thehousing cover 25 have nuts 28 screwed onto them in order for theabove-mentioned components to be clamped in and secured.

It is also the case that the stud-like connecting means 26 and theradial collars 27′ thereof and also the nuts 27″ are formed from a hardand tough material such as ST 50 steel, and these accordingly form,together with the cage plates 18 and 24, a cage 29 which serves forprotecting the housing 2 and the fan-portion components, for example thehousing cover 25, in the event of the impeller 8 bursting.

The gap s which is left between the two cage plates 18 and 24, andthrough which in particular the diffuser blades 22 pass, covers onlypart of the height h of the impeller blades 16, that is to sayapproximately the region of half the height h and thus at least theheight h′ of the blades 16 at their greatest radial extent, that is tosay in the vicinity of the foot region of the impeller 8.

The above-described configuration of the cage 29 formed from hard andtough material ensures that, in the event of the impeller 8 bursting,large, and thus dangerous, fragments are not slung radially outward bycentrifugal force. It also counteracts any fragment-induced damage tothe housing cover 25 and/or the housing 2 or the cooling-channel housing14, which is disposed on the underside of the gap s. The cage plates 24here serve as a protective shield against destruction-inducedenlargement of the radial gap. The respectively rearward support of thecage plates 18 and 24 on the collars 27′ and nuts 27″ reliablycounteracts any gap enlargement between the cage plates 18 and 24 (cf.FIG. 8 a).

In particular for the purpose of cooling the electric drive 4, theradial fan 1 has a cooling system, which is substantially divided intwo. A primary cooling system is therefore provided, and this uses aninternal gas flow which is closed off hermetically in the outwarddirection. A secondary cooling system is in the form of a water coolingmeans which, passing through the housing 2, is channeled outward, thewater being delivered there by corresponding pumping means or the like.

The second cooling medium, which is designated by K₂ in the drawings, isthe above-mentioned internal gas flow of the primary cooling system. Inthis case, the difference in pressure, during operation of the radialfan 1, between the region of the radially outer periphery of theimpeller 8 and the radially outer outlet region of the annular gap 21 ofthe diffuser is used in order to create an automatic flow which has noactive assistance. A lower pressure P′ thus prevails in the region ofthe radially outer periphery of the impeller 8 than at the radiallyouter outlet region of the annular gap 21. The pressure P, which isincreased there as a result of the diffuser blades 22, correspondsapproximately to twice the radially inner pressure P′.

The resulting difference in pressure is used in order to branch off apartial gas stream T from the main gas stream H which passes outradially, this partial gas stream then being fed via appropriate paths30 in order to cool the electric drive 4. Re-entry of the partial gasstream into the main gas stream H is effected in the region of the lowerpressure P′, that is to say in the region of the radially outerperiphery of the impeller 8, gas circulation being achieved as a result.

The gas is preferably helium and/or nitrogen and/or air and/or a mixtureof two or more of the gases mentioned.

The above-described paths 30 for the second cooling medium K₂ runsubstantially parallel to the shaft axis x and, furthermore, extendsubstantially between the cooling-channel housing 14 and the foot part 9of the housing 2.

On the upper side, which is directed toward the cage plate 18, thecooling-channel housing 14 is provided with a plurality of, in theexemplary embodiment illustrated, with seven, labyrinthine housing paths31 which open out in the radially outward direction, via a respectivebranch channel 32, in the radially outer region of the annular gap 21,in which the increased pressure P prevails during operation of theradial fan 1. The other end of each labyrinthine housing path mergestoward the inside of the cooling-channel housing 14, as seen in theradial direction, into an axial channel 33, which is connected to acorrespondingly positioned axial bore 34 in the annular part 15, thisbeing associated with the housing 2.

The labyrinthine paths 31 take a meandering course as seen in a planview of the cooling-channel housing 14, such a labyrinthine path 31being provided in each interspace between two circumferentially adjacentstud-like connecting means 26.

The housing wall 35, which encloses the electric drive 4, is of solidconfiguration, and accordingly also forms a cooling body.

In extension of the axial bores 34 of the annular part 15, coolantchannels 36 extend in the housing wall 35. These channels run parallelto the shaft axis x in the region of the cross-sectionally roundedcorner regions between two adjacent plane surfaces 3. As can be seen, inparticular, from the sectional illustration in FIG. 10, each cornerregion of the housing wall 35 is assigned three such coolant channels36, which are each connected to a corresponding number of bores andchannels in the annular part 15 and/or in the cooling-channel housing14.

As has been mentioned, primary cooling takes place by means of thedifferential-pressure-controlled partial gas stream T separated off fromthe main gas stream H. This partial gas stream T, branching off from theradially outer position of the annular. gap 21 in the region of thediffuser 20, is channeled radially inward through the labyrinthine paths31 of the cooling-channel housing 14. The partial gas stream T thenpasses through the axial channels 33 of the cooling-channel housing 14,the axial bores 34 of the annular part 15 and the coolant channels 36 inthe region of the housing walls 35 in order, finally, to be deflectedthrough approximately 180°, by means of paths which have not beenillustrated specifically, in that end of the housing 2 which is directedaway from the impeller 8, in the region of the foot part 9 providedthere. Part of the partial gas stream T is then channeled through theinterspace between the rotor 6 and stator 5. A further part of the gasstream also flows through the drive shaft 7, which is formed as a hollowshaft, in order to pass out radially outward into the interior of thehousing 2 in the region beneath the impeller 8. From this housinginterior, the partial gas stream T passes back, in the low-pressureregion P′ in the vicinity of the radially outer periphery of theimpeller 8, into the main gas stream which is to be compressed.

First cooling of the partial gas stream T takes place by way of contactwith the housing wall 35. The cooling effect is increased further by theactive, secondary cooling system. This is a water cooling means. Thisfirst cooling medium, which is designated by K₁, is channeled throughpaths 37 which, in the exemplary embodiment illustrated, runperpendicularly to the paths 30 of the second cooling medium K₂. Thesepaths 37 thus run in the circumferential direction in relation to theshaft axis x, in doing so extending over an axial region which coversapproximately the stator region.

In order to form the paths 37, in first instance chamber-like housingrecesses 38, which initially open outward in cross-section, are providedin the outer wall of the housing 2, associated with the plane surfaces3. These housing recesses are accordingly positioned in each casebetween two circumferentially adjacent, rounded corner regions of thehousing wall 35, in which corner regions—as has been mentioned—the paths30 for the second cooling medium K₂ are placed, the paths 30 runningperpendicularly to these paths 37.

The, in the exemplary embodiment illustrated, four chamber-like housingrecesses 38, which are offset at an angle of 90° in relation to oneanother, are flow-connected to one another by bores 39 which are placedsuch that housing material remains both in the direction of the stator5, which is disposed inside the housing, and in the direction of thegas-flow paths 37, which run in the corner regions of the housing wall35. Accordingly, the paths 37 of the first cooling medium K₁ and thepaths 30 of the second cooling medium K₂ are separated from one anotherby uninterrupted material walls 40.

As an alternative to the bores 39 proposed, the connections between thehousing recesses 38 may also be achieved in the casting process.

The flow-connection between the housing recesses 38 results in a path 37for the first cooling medium K₁ which runs all the way around thecircumference.

As seen in the axial direction, the chamber-like housing recesses 38 arebounded by integral walls 41 of the housing 2. The housing recesses 38are delimited in the radially outward direction by means of plate-likecoverings 42 which are secured in a sealing manner, in the region of theadjacent housing-corner formations, along the recess periphery runninground the outer wall of the housing 2.

A covering 42 here is provided with a connection 43 in order to form acooling-medium infeed 44. The covering 42 which is located diametricallyopposite this covering likewise has a connection 43, for forming acooling-medium discharge 45.

As can also be seen, in particular, from the illustrations in FIGS. 9and 10, the bores 39, which connect the chamber-like housing recesses38, are configured as slot-like bores which extend approximately overthe entire axial length of the stator 5, which is disposed in thehousing interior.

The paths 37 of the first cooling medium K₁ (water circuit) are disposedfurther toward the inside, as seen in the radial direction, than thepaths 30 of the second cooling medium K₂ (gas circuit), at least in theregion between the chamber-like housing recesses 38, that is to say inthe region of the solid housing-corner regions which accommodate thepaths 30.

The paths 30 and 37 of the two cooling media K₁ and K₂ run at an anglein relation to one another, without any sealing means being used forseparating the paths 30 and 37 from one another. This separation isachieved merely by way of intact housing material.

FIGS. 11 to 13 show an alternative embodiment of the radial fan 1, inparticular of the housing 2. The cage, the diffuser and the housingcover have been left out of the illustration for this embodiment.

The functioning and the general course taken by the cooling circuitscorrespond to those of the exemplary embodiment described above.

The essential difference resides in the overall configuration of thehousing 2. In this second exemplary embodiment, this housing issubstantially cylindrical throughout with a round cross-section. Fourcircumferentially uniformly distributed, chamber-like housing recesses38 are formed in the solid housing wall 35 and intact housing-wallportions, which accommodate axially running paths 30 for the secondcooling medium K₂, remain between them—as seen over the circumference.These paths 30 are associated with a radially outer region of these wallportions. The bores 39, which connect the chamber-like housing recesses38, are provided in the radially inner region of these wall portions. Ascan be seen, in particular, from the perspective illustration in FIG.14, each chamber-like housing recess 38 has a plurality of bores 39which are disposed one behind the other in the direction of extent ofthe shaft axis x, which bores 39, in accordance with the sectionalillustration in FIG. 11, cover substantially the region of extent of thestator as seen in the same direction.

In this second embodiment, the covering 42, which closes thechamber-like housing recesses 38, is formed as a tubular part 46 whichencloses the housing 2 and can be secured on the outside of the housingwall 35 by correspondingly positioned sealing means.

The cooling-medium infeed 44, on the one hand, and the cooling-mediumdischarge 45, on the other hand, are formed at two diametricallyopposite regions, each associated with a chamber-like housing recess 38.

All features disclosed are (in themselves) pertinent to the invention.The disclosure content of the associated/attached priority documents(copy of the prior application) is hereby also included in full in thedisclosure of the application, also for the purpose of incorporatingfeatures of these documents in claims of the present application.

1. Radial fan (1), preferably high-speed radial fan, having an impeller(8) and a housing (2), the housing (2) accommodating a rotor (6) and astator (5) of an electric drive (4) for the impeller shaft (7), acooling means being provided, and paths (30, 37) being provided in thehousing (2) for a first cooling medium (K₁) and a second cooling medium(K₂), for cooling of the second cooling medium (K₂) by the first coolingmedium (K₁) by means of the housing (2), wherein the second coolingmedium (K₂) is based on an internal gas flow which is closed offhermetically with respect to the exterior, in that the paths (30, 37)are separated from one another by uninterrupted material walls (40) ofthe housing (2) and, for this purpose, are formed by the casting processand/or as bores, the separation between the paths being achieved merelyby way of intact housing material.
 2. Radial fan according to claim 1,wherein the paths (30, 37) in the housing (2) run at an angle inrelation to one another.
 3. Radial fan according to claim 1, wherein thepaths (30, 37) run perpendicularly to one another.
 4. Radial fanaccording to claim 1, wherein the paths (30, 37) of the first coolingmedium (K₁) are disposed in the outer wall of the housing (2), in across-sectionally chamber-like housing recess (38).
 5. Radial fanaccording to claim 4, wherein two circumferentially distributed paths(37) of the first cooling medium (K₁) are routed in a chamber-likehousing recess (38).
 6. Radial fan according to claim 4, wherein threeor more chamber-like housing recesses (38) are provided over thecircumference.
 7. Radial fan according to claim 4, wherein thechamber-like housing recesses (38) are bounded in the axial direction ofthe housing (2) by integral walls (41) of the housing (2).
 8. Radial fanaccording to claim 4, wherein the chamber-like housing recesses (38) areclosed by a covering (42) extending in the axial direction of thehousing (2).
 9. Radial fan according to claim 8, wherein the covering(42) is in the form of a tubular part (46) which encloses the housing(2).
 10. Radial fan according to claim 4, wherein one chamber-likehousing recess (38) is formed as a cooling-medium infeed (44) and onechamber-like housing recess (38) is formed as a cooling-medium discharge(44).
 11. Radial fan according to claim 1, wherein the housing (2) iscylindrical, one end being associated with the impeller (8) and theother end being closed via a foot part (9).
 12. Radial fan according toclaim 11, wherein the other end has a stepped formation, and the footpart (9) is stepped correspondingly.
 13. Radial fan according to claim4, wherein the paths (37) of the first cooling medium (K₁) run furthertoward the inside, as seen in the radial direction, than the paths (30)of the second cooling medium (K₂) at least in the region between thechamber-like housing recesses (38), the second cooling medium (K₂) alsopassing through the interior of the housing (2).
 14. Radial fanaccording to claim 1, wherein the paths (37) of the first cooling medium(K₁), predominantly for the purpose of dissipating the power loss of thestator (5), are brought close to the stator (5).
 15. Radial fanaccording to claim 1, wherein axial bores are provided, which correspondto the paths (30) for the second cooling medium (K₂) and are used foraccommodating electric lines.
 16. Radial fan (1), preferably high-speedradial fan, having an impeller (8) and a housing (2), the housing (2)accommodating a rotor (6) and a stator (5) of an electric drive (4) forthe impeller shaft (7), a cooling means being provided and, furthermore,cooling in particular of the drive (4) being achieved by a partial gasstream (T) separated off from the gas which is to be compressed, whereinthe partial gas stream is channeled, following separation, into paths(31) of a cooling-channel housing (14), which, for its part, is activelycooled at least indirectly.
 17. Radial fan according to claim 16,wherein the housing paths (31) are labyrinthine.
 18. Radial fanaccording to claim 16, wherein the housing paths (31) lead radiallyinward from the outside.
 19. Radial fan according to claim 16, whereinthe partial gas stream (T) is branched off from the main gas stream (H)radially outside the impeller (8), in the region of a diffuser (20). 20.Radial fan according to claim 19, wherein the partial gas stream (T)then passes through the housing wall (35) of the housing region whichaccommodates the electric drive (4).
 21. Radial fan according to claim16, wherein it is at that end of the electric drive (4) which isdirected away from the impeller (8) that the partial gas stream. (T) ischanneled out of the housing (2) into the interspace between the stator(5) and rotor (6).
 22. Radial fan according to claim 16, wherein thedrive shaft (7) is in the form of a hollow shaft, and wherein it is atthat end of the electric drive (4) which is directed away from theimpeller (8) that the partial gas stream (T) is channeled out of thehousing (2) into the drive shaft (7).
 23. Radial fan according to claim16, wherein the partial gas stream (T) is channeled back into the maingas stream (H) at the radially outer periphery of the impeller (8). 24.Radial fan according to claim 16, wherein the active cooling means ofthe housing (2) is in the form of a water cooling means.
 25. Radial fanaccording to claim 16, wherein the gas consists of helium and/ornitrogen and/or is air and/or is a mixture of two or more of the gasesmentioned.